Known hybrid cables include a plurality of telecommunication fiber-optic cables and a plurality of electrical power cables within a single outer cable jacket. Such hybrid cables may be used as feeder cables in cellular systems to connect base stations (BTSs/NodeBs/eNodeBs) to transceivers or remote radio heads (RRHs), thereby providing power to RRHs and supporting radio frequency (RF) signal transmissions to and from RRHs.
FIG. 1 shows a conventional hybrid cable 1. The cable 1 includes a main body portion 1a and a termination portion 1b adjacent to the main body portion 1a at an end of the hybrid cable 1. The termination portion 1b may be used to connect the hybrid cable 1 to a transceiver or RRH (not shown), for example. Another termination portion (not shown) may be provided at an opposite end (not shown) of the hybrid cable 1 for connecting the hybrid cable 1 to a base station, for example.
Continuing with reference to FIG. 1, the hybrid cable 1 includes a plurality of fiber-optic cable pairs 10 including a first fiber-optic cable 12 and a second fiber-optic cable 14, and a plurality of DC power cable pairs 20 including a first power cable 22 of a first polarity and a second power cable 24 of a second polarity. At the main body portion 1a of the hybrid cable 1, the fiber-optic cable pairs 10 and the power cable pairs 20 are disposed within a main jacket 2. The plurality of fiber-optic cables 10 are further retained within a fiber-optic cable jacket or channel 6 inside of the main jacket 2. An armor member 4 is disposed within the main jacket 2 throughout the main body portion 1a, and surrounds the fiber-optic cable jacket or channel 6 and the power cable pairs 20.
The termination portion 1b includes a transition section T adjacent to the main body portion 1a that provides a protective transition region between the main body portion 1a and the termination portion 1b. The armor member 4 terminates part way through the transition section T. The fiber-optic cable pairs 10 and the power cable pairs 20 extend axially beyond the armor member 4 from the area at which the armor member 4 terminates. A first, main break-out boot 30 may be attached to the outer jacket 2 at an end of the main body portion 1a of the hybrid cable 1, and may cover the armor member 4, the fiber-optic cable pairs 10 and the power cable pairs 20 at the transition section T. The main break-out boot 30 defines one or more openings 32 through which the fiber-optic cable pairs 10 and the power cable pairs 20 extend outside of the main jacket 2, the armor member 4 and the main break-out boot 30 in the termination portion 1b of the hybrid cable 1. The power cable pairs 20 extend separately from each other at the termination portion 1b of the hybrid cable 1. A second, fiber-optic cable break-out boot 40 may be attached to an end of the fiber-optic cable jacket 6 at the termination portion 1b, outside of the opening(s) 32 of the main break-out boot 30. The second break-out boot 40 may include one or more openings 42 through which the fiber-optic cable pairs 10 extend separately from each other outside of the fiber-optic cable jacket or channel 6.
A fiber-optic connector 50 may be attached to the end of each fiber-optic cable 10 at the end portion 1b of the hybrid cable 1 for connecting each fiber-optic cable pair 10 to a RRH. Each of the power cable pairs 20 may be connected to a ‘RRH by a respective power cable connector (not shown) at the end portion 1b of the hybrid cable 1. Additional shielding and grounding components (not shown) may be added to each of the power cable pairs 20 at the termination portion 1b of the hybrid cable 1.
The additional shielding added to each of the power cable pairs 20 at the termination portion 1 of the hybrid cable 1 presents a challenge with regard to joining the armor member 4 to the additional shielding to maintain full shielding and grounding throughout the hybrid cable 1. One existing solution to this problem is to use power cable pairs 20 that are individually shielded throughout their entire lengths. However, providing such full-length shielding is expensive and adds substantial weight to the hybrid cable 1, increases the size (diameter) of the hybrid cable 1, and adds significant expense to manufacturing the hybrid cable 1.
An alternative existing solution to the problem of joining the armor member 4 to the additional shielding in the termination portion 1b is to bond shielding components in the termination portion 1b to the armor member 4 through welded connections. However, this solution requires welding of dissimilar metals and subjects the heat-sensitive fiber-optic cables 12, 14 to a high amount of heat.
In view of the above, it is desirable to provide an optical electrical hybrid cable that provides effective shielding and grounding of power cables where the power cables extend outside of a main jacket of the hybrid cable. It is further desirable to provide such a hybrid cable using a minimum amount of additional shielding material in order to minimize the size, weight and cost of the hybrid cable.